Multi-piece truss legs and related couplers

ABSTRACT

A two-piece truss leg with an articulating coupler for an A-frame-shaped truss foundation system for single-axis trackers. The coupler is attached to the head of each screw anchor to enable it to be driven. A connection portion extends above the coupler and is received within an open end of an upper leg to allow the upper leg to be misaligned with respect to it corresponding screw anchor.

CROSS REFERENCE TO RELATED APPLICATIONS

This claims priority to U.S. Provisional Patent Application No.62/727,456, titled, “Foundation piers for axial solar arrays and relatedsystems and methods,” filed on Sep. 5, 2018, U.S. Provisional PatentApplication No. 62/745,188, titled “Optimized A-frame foundations foraxial solar arrays and related systems and methods,” filed on Oct. 12,2018, and U.S. Provisional Patent Application No. 62/801,604, titled,“Articulating pile couplers and related systems and methods,” filed onFeb. 5, 2019, the disclosures of which are hereby incorporated byreference in their entirety.

BACKGROUND

Until recently, single-axis solar trackers have been built predominatelyon monopile foundations. Monopiles consist of individual beams beateninto the ground with a pile driver at regular intervals along anintended North-South axis of the tracker torque tube. The monopileparadigm requires that each beam be over-specified in order to supportnot only the weight of the tracker system (torque tube, panels, motorsand mounting hardware) but also to withstand bending moments introducedby wind striking the array. Because single structural members arerelatively poor at resisting bending, much larger beams must be usedthan that required to support the weight of the tracker system alone.Therefore, monopiles are inherently wasteful relative to foundationsystems that don't need to resist bending.

To address this inefficiency, the applicant and inventors of thisdisclosure have proposed a truss foundation system that uses an A-frameto support the tracker torque tube and bearing assembly. The system isknown commercially as EARTH TRUSS. A-frames are advantageous becausethey translate lateral loads into axial forces of tension andcompression rather than bending. Since single structural members arerelatively good at resisting lateral loads, smaller foundationcomponents may be used to support single-axis trackers, relative tomonopiles, saving steel.

The EARTH TRUSS foundation is constructed by driving a pair of adjacentscrew anchors into the ground so that they are angled towards oneanother. This may be done, for example, with a rotary driver or screwdriving machine. The machine may be a purpose-built device or anattachment to an excavator or other piece of general-purpose heavyequipment. Once the adjacent screw anchors are driven to their targetdepth, upper legs are joined to each screw anchor, and an adapter,bearing adapter or other assembly connects the free ends of each upperleg to complete the truss and to provide support for the trackercomponents.

Whether A-frames or monopiles are used, adherence to positionaltolerances is important to prevent undue stress on the tracker torquetube. A-frames present unique challenges relative to monopiles becausetwo separate piles are driven into the ground in a substantially commonEast-West plane but at non-plumb angles on either side of theNorth-South line of the torque tube. Even with machine automation, it ispossible that the respective axes of two adjacent piles do not intersectbecause the piles are driven offset (i.e., out of plane to one another).Alternatively, in some cases they may intersect but at a point below orabove the desired intersection height. Just as with monopiles,misalignment of foundation components from their intended axes, mayinduce strain on the torque tube and even make it impossible to installtracker components. To that end, the focus of this disclosure is oncomponents and systems for correcting for misalignment betweenfoundation components in truss foundations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is perspective view of a portion of a single-axis trackersupported by A-frame-shaped truss foundations according to variousembodiments of the invention;

FIG. 2A is an end view of the single-axis tracker shown in FIG. 1;

FIG. 2B is an end view of another single-axis tracker supported by anA-frame-shaped truss foundations according to various embodiments of theinvention;

FIG. 2C is an end view of yet another single-axis tracker supported byan A-frame-shaped truss foundations according to various embodiments ofthe invention;

FIG. 3 is an A-frame-shaped truss foundation according to variousembodiments of the invention;

FIGS. 4A and 4B show possible misalignment scenarios with an A-framefoundation according to various embodiments of the invention;

FIGS. 5A and 5B show a coupler for a two-piece truss leg according tovarious embodiments of the invention;

FIG. 5C is an assembled truss foundation according to variousembodiments of the invention;

FIGS. 6A-6C are multiple view of a portion of a truss leg according tovarious embodiments of the invention;

FIGS. 6D and E show possible misalignment cases that can be correctedwith the truss leg according to FIGS. 6A-C;

FIG. 6F is corrosion resistant sleeve for use with the truss leg ofFIGS. 6A-C;

FIGS. 7A-C show incremental steps of assembly of a two-piece truss legaccording to various embodiments of the invention;

FIGS. 8A-D show incremental steps of assembly of another two-piece trussleg according to various embodiments of the invention; and

FIGS. 9A-C show incremental steps of assembly of yet another two-piecetruss leg according to various embodiments of the invention.

DETAILED DESCRIPTION

The following description is intended to convey a thorough understandingof the embodiments described by providing a number of specificembodiments and details involving articulating pile-to-pile interfacesfor A-frame foundations. It should be appreciated, however, that thepresent invention is not limited to these specific embodiments anddetails, which are exemplary only. It is further understood that onepossessing ordinary skill in the art in light of known systems andmethods, would appreciate the use of the invention for its intendedpurposes and benefits in any number of alternative embodiments,depending upon specific design and other needs.

As discussed in the Background, the inventors and applicant of thisdisclosure have proposed an alternative to plumb monopile foundationsthat aims to significantly reduce the total amount of steel required tosupport single-axis trackers and other axial solar arrays. Thisalternative foundation system, referred to commercially as EARTHTRUSS™,consists of a pair of sloped legs extend above and below ground and arejoined at the apex with an adapter, bearing assembly, or other torquetube support element to form a truss. The truss legs are substantiallyaligned on either side of the torque tube so and ideally oriented tothat an imaginary line through their respective centers of massintersects at a point in space that overlaps with the tracker's axis ofrotation.

The truss architecture offers several advantages over conventionalmonopiles foundations. First, if properly designed, the A-frame willtranslate lateral loads into axial forces of tension and compression inthe legs rather than bending. The A-frame or truss directs lateral loadsalong the axis of the legs where it is best applied. Therefore, the sizeand gauge of the steel that makes up the legs may be much smaller thanan equivalent monopile. Also, without needing to resist bending, thelegs do not need to be driven as deep as conventional monopiles. Thissaves steel but also reduces the likelihood of encountering a refusal. Arefusal occurs when additional impacts of a pile driver fail to resultin additional embedment of the pile. Usually, this is the result ofstriking rock or cementious soil and requires an expensive,labor-intensive mitigation process. The shallower piles are driven, theless likely it is that they will encounter rock or cementious soil.

Turning now to FIG. 1, this figure shows a portion of a single-axistracker supported by several A-frame-shaped truss foundations accordingto various embodiments of the invention. Each foundation 100 consists oflegs 110 extending above and below ground and joined together withadapter 115. Bearing assemblies 120 sit atop each adapter 115 and torquetube 130 passes substantially orthogonally through each bearingassembly, enabling it to rotate about its own axis. Solar panels 140 areattached to torque tube 130 via mounting brackets 135. This exemplarytracker system is a bottom-up design where the torque tube is supportedfrom below by a bearing housing assembly that rests on the adapter.Other tracker systems may employ a top-down design where the torque tubehangs from a bearing pin received in the bearing assembly so that thetorque tube can sweep through an arc like a pendulum. In such systems,the drive motor is offset from the torque tube's main axis so that thetracker's axis of rotation. Bearing assemblies are still attached to thehead of each pile, but the axis of rotation is offset from the torquetube's main axis. One such top-down tracker system is disclosed, forexample, in U.S. Pat. No. 10,222,446, which is hereby incorporated byreference in its entirety. The various embodiments of the invention arecompatible with bottom-up as well as top-down or off-set single-axistrackers.

FIGS. 2A-2C are end views of various tracker systems supported by anA-frame-shaped truss foundation according to the various embodiments ofthe invention. Starting with 2A, this figure shows and end view of thetracker system of FIG. 1. Each leg 110 consists of screw anchor 111 andupper leg 112. In various embodiments, each screw anchor 111 is drivenuntil only the end extends above-ground so that it can be connected toone of the upper legs. Upper legs 112 are joined by adapter 115 to forma rigid A-frame structure which, in turn supports bearing assembly 120.In various embodiments, screw anchors 111 may be driven at symmetricangles ±θ to one another (e.g., at ±60-degrees with respect tohorizontal). Adapter 115 in this example, has a pair of connectingportions extending down and away from each other at an angle and spacingthat match the angle and spacing of legs 110.

Turning to FIG. 2B, this figure shows another single-axis tracker systemsupported by an A-frame-shaped truss foundation according to variousembodiments of the invention. The tracker system shown here is atop-down design where the torque tube drive motor is offset from themain axis of the tube so that the tube swings through an arc rather thanrotating about its own axis. As with the system in 2A, tracker 200 issupported by two-piece truss legs 110 consisting of screw anchors 111and upper legs 112. However, instead of a separate bearing assembly, thesystem of 2B uses single bearing adapter 200 to perform both functions.Bearing adapter 200 consists of symmetric S-shaped arms 208interconnected by bridge portion 210. Bearing pin 220 passes through acylindrical bearing in the approximate middle of bridge portion 210.Hanger clamps suspend torque tube 130 from bearing pin 220. SymmetricS-shaped arms 208 define an opening for torque 130 to swing within asthe motor moves tube 130 from an East-facing orientation to aWest-facing one.

FIG. 2C shows another bottom-up style single-axis tracker systemsupported by an A-frame-shaped truss foundation according to variousembodiments of the invention. In this system, truss legs 110 are joinedby adapter 300. Adapter 300 approximates H-pile flanges with verticalmounting flanges 310 interconnected by bridge portion 312. Flanges 310terminate into symmetric wings that support connecting portions 315.Pile cap 320 attaches to flanges 310 and bearing assembly 325 sit onpile cap 320. Torque tube 130 rotates about its own axis within bearing325.

Although they are all different, each of the systems shown in FIGS. 2A-Cinclude truss legs and adapters that orient the legs to substantiallypoint at the rotational axis of the system. This is shown by the dottedlines in the figures extending from the approximate center of mass ofeach leg to the rotational axis of the system. In 2A, these lines extendto the center of torque tube 130 which is also the center of bearingassembly 115. In 2B, the lines extend to bearing pin 220 in bridgeportion 210, and in 2C, they also extend to torque tube 130 at thecenter of bearing assembly 325.

Turning to FIG. 3, this figure shows the foundation system used tosupport the various trackers in FIGS. 2A-C with the adapters and trackercomponents removed. If the piles are aligned with respect to the torquetube, they will point at a common intersection point labeled “WP” in thefigure. This point is referred to herein as the apex or work point ofthe truss and represents the ideal place to apply lateral loads toprevent the introduction of bending moments. The location of the workpoint relative to the ground will vary with truss leg angle θ/top angleα as well as with the spacing between the legs at the point where theyare driven into the ground. The steeper the leg angle/smaller the topangle, or further apart the screw anchors are when driven into theground, the higher the work point will be.

In a single-axis tracker, forces are translated to the foundation viathe rotational axis of the system (i.e., the point where rotating partscontact the non-rotating parts rotate about or within). In mostsingle-axis tracker systems, where a torque tube is captured within acircular bearing, the torque tube itself defines the axis of rotation solateral forces are transferred to the foundation directly via thebearing assembly surrounding the tube. However, as discussed in thecontext of FIG. 2B, in some trackers, the torque tube is offset from theaxis of rotation and instead swings about a bearing pin above the tube.In this type of tracker, the axis of rotation is about the bearing pinrather than the tube. In either case, when supported by a trussfoundation, the rotational axis should ideally pass through the workpoint to prevent the introduction of bending moments in response tolateral loads, which in turn, will require additional reinforcement toresist. Using more metal to construct the legs is antithetical to thegoal of reducing steel and negates some of the benefits of a trussrelative to monopiles. Because this problem is unique to A-framefoundations, it is not one that tracker makers have needed to designfor, however, even those who have proposed A-frame foundations forsingle-axis trackers in the prior art have failed to recognize thesignificance of alignment and orientation of the rotational axis withthe work point in reducing and ideally eliminating moments.

In order to achieve this, it is important to control the orientation ofthe truss legs with respect to each other as well as with respect to theintended axis of rotation. When installing screw anchors there areseveral possible modes of misalignment that could result in the legs notintersecting at the intended axis of rotation. For example, the screwanchors may be aligned in the East-West direction but oriented atdifferent angles with respect to horizontal. In other words, theirrespective axes do intersect but not at the intended axis of rotation.In other cases, they may be misaligned so that their respective axesdon't intersect. In still further cases, they may be aligned and leaningtoo far North or South so that they intersect at a point below or abovethe desired work point. Any of these situations could introduce a momentto the foundation and/or make it difficult to attach the torque tube andbearing assembly components.

FIGS. 4A and B illustrate two exemplary cases of axial misalignmentbetween screw anchors. In 4A, the actual axis of the left screw anchoris not aligned with the right screw anchor or with respect to thedesired rotational axis because the screw anchor was driven at the wronglocation. The dotted line extending out of each anchor shows that theleft anchor's actual axis is off the ideal and therefore does notintersect the right anchor's axis. In FIG. 4B, the base piles areco-planer, but one has been driven at a steeper angle with respect tohorizontal and therefore the point of intersection is above the desiredrotational axis.

One way to compensate for the possible modes of misalignment shown inFIGS. 4A and B relies on flexibility inherent in two-piece leg paradigm.By building some degree of axial adjustment in the coupling betweenscrew anchors and upper legs, it is possible to redirect the screwanchor's misaligned axis via the upper leg when joining the upper legsto an adapter or to a bearing adapter. To that end, various embodimentsof the invention provide couplers for joining upper legs to driven screwanchors that provide some (e.g. 0 to 10-degrees) of multi oromnidirectional axial adjustment. FIGS. 5A-B show one such coupleraccording to various exemplary embodiments of the invention.

Coupler 160 has a main body portion with a pair of opposing male andfemale portions top and bottom ends respectively. In the figure, toprefers to the portion closest to upper leg 112 and bottom refers to theportion closest to screw anchor 111. Using this reference, the top endof screw anchor 111 is received in a recess in the bottom end of coupler160. Screw anchor 111 is shown as having a substantially uniformdiameter without any modifications to the upper end. In variousembodiments, coupler 160 includes internal stop 165 visible in 5B thatlimits the extent of penetration of screw anchor 111 into the main bodyof coupler 160. It should be appreciated that in other embodiments theorientation of coupler 160 may be reversed so that upper leg 112 isreceived within the body of coupler 160.

In various embodiments, one or more spot welds or continuous welds maybe used to join coupler 160 to screw anchor 111. In various embodiments,the opening in the bottom of coupler 160 is circumscribed by a ledge161. In other embodiments, one or more stops may be formed on the outersurface of coupler 160 in place of ledge 161. In the example of FIGS.5A/B, ledge 161 has several driving features (e.g., notches) formed init that enable a chuck or other driving head of a rotary driver toengage with it while still providing orthogonal surfaces area to limitthe extent of penetration into upper leg 112. These notches areexemplary only. In other embodiments, facets may be cut into ledge 161instead of notches. In still further embodiments, other shapes and/orfeatures may be used. The specific geometry of driving features or stopsin ledge 161 is a design choice.

The top portion of coupler 160 above ledge 161 is referred to generallyas the connecting portion. This portion consists of a pair of opposingtapered or conical surfaces 162/164 projecting above ledge 161. Movingaway from ledge 161, surface 162 increases in outside diameter up to arelative maximum. In this exemplary embodiments, a gap is formed at therelative maximum. Gap 163 is characterized by an outside diameter thatis relatively smaller than surface 162 at its maximum diameter. Taperedsurface 164 begins on the opposing side of gap 163. Surface 164 beginson the other side of gap 163 at its maximum diameter, decreasing asmoving away from gap 163. In various embodiments, gap 163 completelycircumscribes coupler 160. In other embodiments, gap 163 may be formedin one or more distinct locations around the circumference of coupler160. In various embodiments, tapered surfaces 162/164 have slopes thatare symmetric about gap 163, even if they are not the same size. Itshould be appreciated that although tapered or conical surfaces 162/164are shown as continuous that in various embodiments they maybe formed intwo or more distinct sections. Also, one or more gaps may be formedwithin conical surfaces 162/164. Such modifications are within spiritand scope of the various embodiments of the invention.

In various embodiments, and as shown in 5B, upper leg 112 may have aslightly larger outside diameter than screw anchor 111. In variousembodiments, the connecting portion of coupler 160 is received withinthe lower end of upper leg 112. Ledge 161 may act as a stop to limit thedepth of penetration of coupler 160 within upper leg 112, although asdiscussed above, one or more bumps, stops or other structures may beused for this purpose. In various embodiments, at their maximumdiameter, opposing tapered surfaces 162/164 will be slightly smallerthan the inside diameter of upper leg 112 or portion of upper leg 112that engages with coupler 160. In various embodiments, this will enableupper leg 112 to be sleeved over coupler 161 and pivotedomnidirectionally about ledge 161 to be misaligned with the axis ofscrew anchor 111 by an angle d ranging from 0 up to 10-degrees. Themaximum extent of the angle d will be dictated by slope of taperedportions 162/164. As upper leg is pivoted about ledge 161, differentportions of the inside surface of upper leg 112 will contact surfaces162/164. In various embodiments, this may be useful to correct formisalignment of screw anchor 111 with respect to the intended axis ofrotation by effectively redirecting the leg axis. Once the desiredalignment between upper leg 112 and screw anchor 111 has been achieved,a crimping tool or other device may be used to deform upper leg 112 atone or more locations above a gap in coupler 160. In variousembodiments, the void created by gap 163 will provide a place forplastic deformation of upper leg to lock it into place at the desiredorientation.

FIG. 5C shows how alignment may be performed in real-world conditions inaccordance with various embodiments of the invention. Adjacent screwanchors 111 are driven into support ground at the desired locations oneither side of the North-South row where the torque tube will bepositioned and angles to one another to enable their respective axes tointersect at the intended axis of rotation. The specific mechanism andmeans for accomplishing the initial orientation of the machine drivingthe screw anchors so that are aligned with respect to the intended axisof rotation is intentionally omitted here because it is the subject ofother applications. Once screw anchors 111 are driven to the desired ortarget depth, upper legs 112 may be sleeved over respective couplers161. In various embodiments, coupler 161 will provide enough resistanceto keep upper legs 112 in place. Then, adapter 400 is attached to theopposing end of each upper leg. In various embodiments, a jig or otherdevice, such as jig 500 shown in the figure, may be placed atop adapter400. Jig 500 may have one or more magnetic portions to enable it to beselectively attached to adapter 400. The jig shown in this exemplaryfigure has planar portion 510 and laser target 515. In variousembodiments, target 515 may be set to approximate the height aboveadapter 400 of the rotational axis of the intended bearing assembly sothat upper legs 112 may be aligned with the rotational axis. In variousembodiments, a laser guide may be set on the legs or adapter of thepreceding or first installed truss so that subsequent trusses may bealigned to that one. In various embodiments, coupler 160 will allowupper legs 112 to be moved omnidirectionally with respect to coupler160, as well as vertically so that adapter 400 can be oriented to placetarget 515 in the path of laser. Once the desired orientation isachieved, a crimping tool or other device may be used to plasticallydeform upper legs 112 over channel 163 in coupler 160 to preserve theorientation. It should be appreciated that in various other embodiments,jig 500 may also replicate the geometry of the adapter so that upperlegs 112 may be correctly oriented before attaching adapter 400. In suchcases, once the proper leg alignment has been achieved, and upper legs112 crimped, jig 500 may be removed, leaving only upper legs 112extending in free space so that an adapter and bearing assembly, or,alternatively, a bearing adapter may be installed without needing toperform additional laser-based alignment. Micro-adjustments in both theEast-West and vertical directions may be made when the bearingassemblies are attached to adapter 400 to account for tolerances in thetorque tube itself.

Turning now to FIGS. 6A-D, these figures show another coupling systemfor a two-piece truss leg that enables the upper portion to axiallyarticulate with respect to the lower one in any direction in accordancewith various embodiments of the invention. The system shown in thesefigures relies on plastic deformation of the extension pile aboutarticulating joint 172 formed in upper leg 112 proximate to where itcouples to screw anchor 111.

FIG. 6A shows elongated upper leg 112 with articulating joint 172proximate to lower end 171 that connects to screw anchor 111. In thisexample, joint 172 is formed by compressing or pinching upper leg 112around its outer surface to form a circular indentation. In variousembodiments, upper leg 112 has a slightly larger diameter than screwanchor 111 so that it can fit over the top of screw anchor 111. In otherembodiments, they may be the same diameter, but the upper end of screwanchor 111 may be tapered to allow a portion of upper leg 112 to fitover it. In still further embodiments, lower end 171 of upper leg 112may be slightly expanded to allow it to fit over the top end of screwanchor 111. In still further embodiments, the end of upper leg 112 mayfit inside the top end of screw anchor 111.

In the example shown here, articulating joint 172 is a crimpedindentation formed in lower end 171 of upper leg 112. This is arelatively inexpensive method to create an articulating joint relativeto other designs. In addition to providing a pre-stress point forbending upper leg 112, joint 172 functions as a stop, limiting the depthof penetration of screw anchor 111 into upper leg 112. In this example,upper leg 112 includes pin holes 173 for receiving retaining pin 174. Invarious embodiments, retaining pin 174 may be secured with cotter pin175. Alternatively, a different mechanism may be used to secureretaining pin 174. In various embodiments, the top end of screw anchor111 may also have a pair of aligned holes that line up with holes 173when upper leg 112 is sleeved over it.

Once upper leg 112 has been secured to screw anchor 111, applyingpressure to the top end of upper leg 112 will put strain on the crimpedindentation causing it to plastically deform in the direction of theapplied force. The length of the upper leg 112 will function as a leverallowing deformation to occur without machine assistance. A jig or otherdevice, such as jig 500 shown and discussed in the context of FIG. 5Cmay be attached to the free end of adjacent upper legs 112 to enable aninstaller to determine whether adjustment is needed and if, so which legand in which direction it should be made. By applying pressure to thetop end of one or both upper legs, articulating joint 172 will yield,enabling the installer to plastically deform upper leg 112 to achievethe desired orientation. FIG. 6B shows a close-up of lower end 171 ofupper leg 112 including join 172, and FIG. 6C is a partially explodedview of one possible way of connecting screw anchor 111 to upper leg112. It should be appreciated that these are exemplary only and thatother means may be used to physically couple the ends of the two pilestogether.

FIGS. 6D and E show upper leg 112 of FIGS. 6A-C articulating relative toscrew anchor 111 to adjust for axial misalignment of the latter with anintended axis of rotation. In 6D, coupling upper leg 112 to screw anchor111 reveals that the screw anchors are out of plane with one anotherbecause their respective axes do not intersect. Pressing on the top endof each upper leg 112 will deform it about articulating joint 172,enabling them to be re-aligned so that their respective axes intersectat the desired work point or rotational axis as seen in 6E. Plasticdeformation of articulating joint 172 ensures that the correctorientation of upper legs 112 will be preserved for subsequentattachment of adapters, bearing assemblies and/or bearing adapters.

Plastic deformation of joint 172 may have the untended consequence ofcracking or otherwise damaging any corrosion resistant surface formed onupper leg 112 if the surface is unable to plastically deform. Thesesurfaces may include, but are not limited to, zinc, epoxy or polymer. Ifthe corrosion resistant coating is less malleable than the underlyingsteel, plastic deformation of the steel could result in cracks or otherfailures that expose the base metal. In order to mitigate this risk, invarious embodiments, it may be necessary desirable to reinforce joint172. In the example of FIG. 6F, this is done with sleeve 176 made ofrubber, polymer or other suitable UV-resistant material that extendspast either side of joint 172 to provide a water and air-tight seal,protecting an exposed base metal from exposure. In other embodiments, alayer of rubberized paint or other suitable flexible coating may beapplied over joint 172 to protect the underlying metal.

Turning now to FIGS. 7A-C, these figures show a coupling system for atwo-piece truss leg according to various other embodiments of theinvention. In this system, the ends of screw anchor 111 and upper leg112 are modified to facilitate coupling and enable axial misalignment.Screw anchor 111 includes bell-shaped end 180 that terminates withflanges 182 spaced around opening 181. Similarly, upper leg 112 hasfluted end 183 that consists of opposing tapered portions separated by asection of uniform diameter. The first tapered portion acts as a lead-into assist with insertion of the end 183 into opening 181 while theuniform diameter portion helps fluted end 183 seat within opening 181.Locking collar 184 is sleeved down over end 183 to engage with flanges182 on end 180 of screw anchor 111. Locking collar 184 has a centeropening large enough to accommodate the outside diameter of upper leg112 so that it can slide along upper leg 112 without interference. Oncefluted end 183 is inserted into opening 181 of screw anchor 111, lockingcollar 184 is slid down upper leg 112 until flanges 182 of end 180 areoriented into corresponding openings 185 in collar 184. Collar 184 isthen rotated less than one quarter turn to lock it to screw anchor 111.Rotating the collar traps fluted opening 183 of upper leg 112 inbell-shaped opening 181 so that it can resist axial forces and yetarticulating to different angles with respect to screw anchor 111.

The geometry of the system of FIGS. 7A-C allows upper leg 112 to movewithin opening 181 like a ball in a ball and socket joint, enablingupper leg 112 to articulate by several degrees (e.g., 0 to 10-degrees)in any direction without deforming either component or disconnecting onefrom the other. Though not shown in the figure, locking collar 184 mayhave two or more smooth faces on opposing sides of its outer surface toenable an installer to use a tool to torque it down. In variousembodiments, axial adjustments may be made after locking collar 184 hasbeen locked to end 180 of screw anchor 111. In other embodiments, upperleg 112 must first be oriented to the desired angle with respect toscrew anchor 111 before locking collar 184 is locked. Contact betweenfluted end 183 of upper leg 112 in opening 181 may provide enoughresistance to hold upper leg in place as it is oriented to the desiredangle without the aid of locking collar 184. One advantage of thissystem over that of FIGS. 6A-C is that collar 184 may be repeatedlylocked and unlocked with destroying components or compromising corrosionresistant surfaces because it relies on elastic deformation.

Turning to FIGS. 8A-D, these figures show another coupling system forjoining two-piece truss legs for an A-frame foundation according tovarious other exemplary embodiments of the invention. In this system,base pile 111 has an enlarged, bell-shaped end 190 with stamped featuresprojecting out of its surface that form an inlet and ridges to guidefeatures formed in a locking collar into and out of a locked position.End 190 has two or more inlets 192 and corresponding ridges 191 forguiding indentations 197 formed in locking collar 196 to pull the collardown and lock it in place pull the collar down and lock it in place viarecess 193. This captures end 194 of upper leg 112 within bell-shapedend 190 of screw anchor 111. End 194 of upper leg 112 may have a flutedgeometry like that shown in the embodiments of the FIGS. 7A-C, withopposing tapered portions separated by a section of uniform diameter. Invarious embodiments, end 194 of upper leg 112 may have the same shape asend 183 shown in FIG. 7A.

This geometry allows the end 194 of upper leg 112 to fit and articulatewithin bell-shaped end 190 of screw anchor 111. Then, locking collar 196can slide down the shaft of upper leg 112 until it reaches upper end 180of screw anchor 111. Indentations 197 in the outer surface of collar196, corresponding to projections on the inside surface, slide intoinlets 192. A combination of downward pressure and torque allowsprojections 197 to travel along stamped ridges 191, pulling collar 196closer to screw anchor 111 until it reaches stop 193 where it locks intoplace. In various embodiments, this connection resists axial forces oftension and compression while allowing upper leg 112 to be axiallymisaligned with respect to screw anchor 111 via the ball-and-socket-likeinterface between them.

FIG. 8C shows the assembly of FIGS. 8A and B after collar 196 is lockedto screw anchor 111 and 8D is a cross-sectional view revealing thegeometry of system components. The inside surface of collar 196 extendsdown (towards the base pile) only part of the distance of the outsideface. The inside face has canted edges 198 sloping away from the surfaceof fluted portion 194 at an angle that approximates the slope of thefirst taper so that the inside face does not interfere with upper leg112 when collar 196 is pulled closer to screw anchor 111. Removal ofcollar 196 is accomplished by the reverse process: pushing down oncollar 196 until projections 197 exit their respective stops 193 andclear the deepest part of ridges 191 while rotating it until projections197 reach their respective outlets 192.

In some cases, once the correct orientation of the two foundationcomponents has been confirmed, it may be desirable to couple anextension member to screw anchor 111 or, in some cases, an extension legto upper leg 112 without introducing any axial misalignment between thetwo connected components. To that end, FIGS. 9A-C show a system forjoining two foundation components end-to-end without misaligning an axisof one with respect to the other. In other words, this system enablesattachment of one foundation component to another to substantiallyextend the axis of the first component along the same axis.

Rather than modifying or stamping the end of either screw anchor 111 orupper leg 112, each receives insert 600 that consists of body 610,toothed ring 615 and flange 620 surrounding the tooth-shaped ring. Invarious embodiments, insert 600 may be welded to the top end of thefirst foundation component and to the corresponding bottom end of thesecond component to be joined. In various embodiments, they aresubstantially the same dimensions. Once attached, inserts 600 provide apair of symmetric surfaces that allow the two components, in this case,screw anchor 111 and upper leg 112 to be joined end-to-end whilepreventing them from spinning, rotating or articulating with respect toeach other. In various embodiments, when properly oriented, tooth-shapedrings 615 will fit together without any voids. When this happens,respective opposing flanges 620 of the upper and lower inserts willcontact one another in a geometry that minimizes spacing between theflanges 620. In various embodiments, semi-circular snap ring 630 ispress fit over flanges 620 from the side, locking them together into asubstantially unitary structure.

An additional benefit provided by toothed rings 615 is that the fitmentbetween the teeth of the upper and lower inserts enables torque appliedto one foundation component to be transferred to the other component. Invarious embodiments, snap ring 630 elastically deforms under the forceof a tool or other device as it is pressed over adjacent flanges 620 sothat it may be attached and detached multiple times with a set of snapring pliers or other equivalent device.

It should be appreciated that the embodiments described and claimedherein are exemplary only. Those of ordinary skill in the art willappreciate modifications and substitutions that retain the spirit andscope of the invention.

The invention claimed is:
 1. A truss leg for a single-axis trackerfoundation comprising: a first elongated foundation member; a secondelongated foundation member; and a coupler for joining the secondelongated foundation member to the first elongated foundation member sothat an axis through a center of second elongated foundation member canbe misaligned with an axis through a center of first elongatedfoundation member in any direction, wherein the coupler is attached toan end of the first elongated foundation member and includes: (A) atleast one conical surface received within the second elongatedfoundation member; and (B) at least one driving feature to enable thefirst elongated foundation member to be driven into supporting groundwith a rotary driver.
 2. The truss leg according to claim 1, wherein thecoupler enables multidirectional adjustment of the axis of the secondelongated foundation member with respect to the axis of the firstelongated foundation member within a range of 0 to 10-degrees.
 3. Thetruss leg according to claim 1, wherein the at least one driving featurelimits a depth of penetration of the coupler when the second elongatedfoundation member is sleeved over the at least one conical surface. 4.The truss leg according to claim 1, wherein the coupler comprises twoconical surfaces separated by at least one gap, the at least one gapproviding a void for crimping the second elongated foundation memberover the coupler.